An interesting project.

Yes, without a de facto leader for this kind of software, sifting through packages can be a chore.
No expert here, but you might want to look at the free audio software from the Bioacoustics Research Program at the Cornell University Ornithology Lab: Raven Lite, or Canary. They're intended originally for birdsong analysis, but they're general sound laboratories featuring multiple display formats - including spectrograms for studying tone and formants. And with luck, your daughter might be able to elicit some interesting support from her fellow scientists at Cornell.
http://www.birds.cornell.edu/brp/softwareI've played a bit with Raven Lite, but not enough to say anything intelligent. And I'm sure others here will be along with other good suggestions. For example, I forget if Audacity includes spectrograms.
Good luck!
_________________
Vivat diabolus in musica! MTGuru's (old)
GG Clips /
Blackbird ClipsJoel Barish: Is there any risk of brain damage?
Dr. Mierzwiak: Well, technically speaking, the procedure
is brain damage.